1. Field of the Invention
The invention concerns a device for needling of a fiber web.
2. Description of Related Art
In devices for needling of a fiber web, a needle beam, on whose bottom a number of needles are held, is driven in an oscillating up-and-down movement, so that the needles repeatedly perforate the fiber web guided on a substrate. Crank mechanisms are ordinarily used to drive such needle beams, in which an eccentrically rotating eccentric weight for weight balancing is ordinarily compensated by corresponding balancing weights on the crankshaft. The inertial effects, because of the rotating and oscillating weight within the device, can be kept low, so that no inadmissible vibrations in the machine frame occur. In order to achieve higher production speeds during needling of a fiber web, drive concepts of the needle beam are now known, in which a superimposed back-and-forth movement of the needle beam aligned in the horizontal direction is generated relative to the up-and-down movement. Such a device is known, for example, from DE 196 15 697 A1.
In the known device, the needle beam is driven by a vertical drive mechanism in an up-and-down movement and by a horizontal drive mechanism in a superimposed back-and-forth movement. The inertial forces in the device occur both in the vertical direction and in the horizontal direction. To balance the weight and inertia, several balancing shafts are arranged in the known device in the machine frame, which counteract the weight and inertia of the crank mechanisms by oppositely rotating eccentric masses. This form of balancing is technically very demanding and requires significant space requirements within the device. The free weight forces and inertial forces occurring with variable stroke adjustment of the horizontal drive mechanism are particularly problematical, since they increase quadratically with stroke frequency and linearly with stroke height. Higher stroke frequencies and therefore higher production speeds, as well as greater horizontal strokes of the needle beam in the known device, therefore necessarily lead to increased vibrations in the machine frame. Such vibrations, however, are very negative with respect to noise, and especially with respect to product quality.
The task of the invention is therefore to design a device for needling of a fiber web of the generic type, so that balancing of the inertial forces occurring in the vertical and horizontal direction is possible by simple means.
Another objective of the invention is to provide a device of the generic type that permits variable stroke adjustments of the needle beam with relatively large horizontal strokes and high stroke frequencies.